The invention relates to a manipulator which, with the assistance of a control unit, forms an industrial robot for primarily picking purposes. In particular, the invention relates to a manipulator with three arms by means of which a movable member, comprised in the manipulator, is brought to arbitrary positions in space with retained orientation and inclination.
An industrial robot comprises a manipulator and control equipment, whereby the manipulator with the assistance of the control equipment carries out arbitrary operations within a working range. Usually, such a manipulator comprises a plurality of arms which support a hand, on which a tool is arranged. In the majority of robot applications, a traditional six-axis manipulator is used, which exhibits sufficient movability to carry out a wide range of operations with mostly very high accuracy. For certain applications, however, there is a need of a manipulator which has fewer degrees of freedom but which permits faster operations. Such a manipulator may be mechanically connected in such a way that the tool-carrying hand is all the time oriented in space in a predetermined manner.
From U.S. Pat. No. 4,976,582 a manipulator is previously known by means of which a movable element in relation to a stationary element may be moved in a space with retained orientation and retained inclination. The manipulator has three arms which jointly support the movable element. Each of these arms is rotatably journalled in the stationary element around a respective first axis. The arm supports a linkage, one end of which is rotatably journalled in the outer part of the arm, allowing a movement in two degrees of freedom. In its other end, the linkage supports the movable element and is journalled therein, allowing a movement in two degrees of freedom.
The linkage comprises two parallel links and is arranged, together with the arm, such that one of the degrees of freedom of each end of the linkage constitutes a rotation around an axis which is parallel to the first axis of the respective arm. Irrespective of the movements of the arm or the linkage, these three axes of rotation are thus kept in parallel. In this way, the movable element will always have the same orientation and inclination in relation to the stationary element. One condition, however, is that the respective first axes of the arms form an angle with each other.
When working in spaces where there are hygienic requirements, a manipulator may not emit any smell, fluid or dirt which may cause sanitary inconvenience in this space. Activities in such spaces often give off dirt and fluids which accumulate on the manipulator and which are then emitted therefrom. The known manipulator has an open design with a plurality of components. All movable components including the drive means with their motors must be lubricated. In that context, it is unavoidable that lubricant and accumulated dirt are, at some time, emitted from the manipulator. This makes the known manipulator less suitable for use in spaces where hygienic requirements are made.
The object of the present invention is to suggest ways and means of manufacturing a manipulator of the kind described above, which is arranged such that it may be used in spaces with hygienic requirements. The manipulator shall be prevented from giving off smell, fluid or dirt. The manipulator shall be capable of being flushed and still capable of diverting heat given off by the drive means. During start-up of the manipulator in a cold space, the drive means shall be capable of being preheated.
These objects are achieved according to the invention by a manipulator according to the characteristic features described in the characterizing portion of the independent claim 1 and with a method according to the characteristic features described in the characterizing portions of the independent claims 6 and 9. Advantageous embodiments are described in the characterizing portions of the dependent claims.
According to the invention, the above-mentioned objects are achieved by arranging an enclosure forming a closed system surrounding the drive means of the manipulator. Within this enclosure, a coolant, which may be air, is pressed through the motors of the drive means. The coolant then delivers the absorbed heat to an external cooling system. During cold start of the manipulator, heat is instead supplied to the motors via the coolant.
The enclosure is closed with such a tightness that it is capable of being flushed without liquid penetrating into the enclosure and there causing damage to the manipulator. The whole manipulator including the enclosure is formed with smooth surfaces without folds or pockets which may attract dirt. Dirt or liquid, given off from the motors, is collected within the enclosure.